There is no such thing as leg armpit in medicine, it should refer to popliteal fossa. Patients with cysts in popliteal fossa may suffer from swelling and pain and activity limitation when the cysts are large in size, which can be handled by medication and surgery. 1. Swelling and pain: popliteal cysts, which are located at the back of the knee joint, are mostly associated with osteoarthritis, and may cause mild pain and swelling, which can be treated with oral non-steroidal anti-inflammatory drugs such as diclofenac sodium and ibuprofen for pain relief and anti-infection. 2. Activity limitation: popliteal cysts, if continue to increase in size, may lead to limitation of knee joint activities, such as squatting, leg bending and other actions to compress the cyst, which may cause pain, in line with the premise of the indications for surgery, can consider taking the surgical removal of the cysts for treatment. Patients should go to the hospital for examination in time and follow the doctor’s instructions for treatment. Once the cyst size increases rapidly or accompanied by severe pain, abscess and other phenomena, they should consult the doctor in time.